Presence of c-kit positive cells in fetal and adult bovine forestomachs

The interstitial cells of Cajal (ICC) have been reported to regulate gastrointestinal motility. We investigated the distribution and the morphological and morphometric characteristics of the immunohistochemical reaction against c-kit in the forestomachs of fetal, newborn and adult cows. The anti-c-kit reaction revealed different populations of ICC among age groups and organs. ICC were more numerous and smaller in fetuses. Larger ICC were identified in newborns, except for those in the rumen. During the earliest stages of development, ICC were abundant in the inner layer of the muscularis and were consistently associated with this layer. In all samples, ICC were found in the outer layer of the tunica muscularis. ICC were found between the two muscle layers in the omasum at all ages; however, they were identified only in the rumen of the adult. Our study demonstrated that ICC are present in the forestomach of bovines.     

Microsatellites from genes show polymorphism in two related Oreochromis species

Six microsatellites were detected in the IGF‐II, GH2, prolactin I and insulin genes of Mozambique tilapia (Oreochromis mossambicus) and Nile tilapia (Oreochromis niloticus) by screening DNA sequences deposited to GenBank. Genotyping of 24 individuals from each species revealed that all six microsatellites were polymorphic in both species. In Mozambique tilapia the number of alleles ranged from 3 to 17 (average 9.8), whereas in Nile tilapia the range was 4–21 (average 10.5). The range of expected heterozygosity values were 0.44–0.95 (average 0.79) in Mozambique tilapia, and 0.52–0.96 (average 0.73) in Nile tilapia.     

Novel Microsatellites from Asian Sea Bass (Lates Calcarifer) and Their Application to Broodstock Analysis

We isolated novel dinucleotide, trinucleotide, and tetranucleotide microsatellites from the genome of Asian sea bass (Lates calcarifer). Two genomic DNA libraries were established, one was enriched for (CA)n repeats, while the other for (GATA)n, (GACA)n, and (AAC)n repeats. Sixty clones containing an insert between 250 and 1000 bp in size were sequenced from each library; altogether 50 (43%) of them contained microsatellites. Forty microsatellites were characterized in 16 unrelated Asian sea bass individuals. Twenty-eight of them (70%) showed specific amplification and polymorphism. The allele number per loci varied between 2 and 20 with an average of 5.3, while expected heterozygosity ranged from 0.31 to 0.95 with an average of 0.64. At some loci allele sizes spread over a wide range (>100 bp). No significant correlation (r = 0.23, df = 31, P > 0.05) was found between the repeat number and the number of alleles. A whole broodstock containing 170 individuals was analyzed by using 8 selected polymorphic microsatellites. The average number of alleles per locus was 11.8 (range, 4–21). The expected heterozygosity ranged from 0.57 to 0.90 with an average of 0.75, while the fixation index was 0.02. Genetic similarity between individuals ranged from 0 to 0.72. Comparison of allele frequencies between the broodstock and the 24 nonrelated individuals revealed some unique alleles.     

Beta1-class integrins regulate the development of laminae and folia in the cerebral and cerebellar cortex

Mice that lack all beta1-class integrins in neurons and glia die prematurely after birth with severe brain malformations. Cortical hemispheres and cerebellar folia fuse, and cortical laminae are perturbed. These defects result from disorganization of the cortical marginal zone, where beta1-class integrins regulate glial endfeet anchorage, meningeal basement membrane remodeling, and formation of the Cajal-Retzius cell layer. Surprisingly, beta1-class integrins are not essential for neuron-glia interactions and neuronal migration during corticogenesis. The phenotype of the beta1-deficient mice resembles pathological changes observed in human cortical dysplasias, suggesting that defective integrin-mediated signal transduction contributes to the development of some of these diseases.     

Rapid Isolation of DNA from Fresh and Preserved Fish Scales for Polymerase Chain Reaction

We developed a simple and inexpensive method to extract DNA from fresh and preserved fish scales. The procedure is based on boiling the scales in 5% Chelex 100, followed by digestion with proteinase K and subsequent absorption of genomic DNA using silica. A single fresh scale from larger species (e.g., tilapia) or a few scales from smaller species (e.g., 4 scales from zebrafish) provide over 200 ng of DNA, enough for at least 40 polymerase chain reaction amplifications. The procedure is applicable for DNA isolation not only from fresh and ethanol-preserved scales, but also from dried and formaldehyde-treated samples, and thus might be useful for investigating specimens stored in museums and other collections. Since the removal of a few scales is a gentle means of sample collection, this technique will allow analysis of genetic diversity, mating systems, and parentage in populations of endangered or ornamental fish with minimal experimental influence. Received November 6, 2000; accepted February 26, 2001.     

Characterization of Microsatellites in the IGF-2 and GH Genes of Asian Seabass (Lates calcarifer)

Four microsatellites were identified by screening the DNA sequences of Asian seabass (Lates calcarifer) deposited to GenBank. Two markers each are located in the growth hormone gene (GH) and in the insulin-like growth factor II gene (IGF-2), respectively. The markers were characterized by genotyping 34 Asian seabass individuals. All 4 microsatellites showed polymorphism: the number of alleles per locus ranged from 2 to 11 (average, 5.0), while the expected heterozygosity ranged from 0.51 to 0.85 (average, 0.63) at the 4 loci. Cross-priming with all 4 primer pairs was tested in species belonging to 5 different genera, but no bands were amplified. These microsatellites are the first genomic DNA markers characterized in L. calcarifer; thus they may be valuable for research and aquaculture production of this species. Received April 10, 2000; accepted July 13, 2000.